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Culturing Volvox and Spirogyra Green Algae
BACK TO CULTURING PROTIST Background Algae are a special group of organisms that are found nearly everywhere—in oceans, freshwater lakes and streams, damp soil, in ice, on rocks, and in the air. Algae are photosynthetic organisms that produce most of the Earth’s oxygen. Most marine and aquatic food chains rely greatly on algae. They grow in very diverse environments and under a variety of conditions. Therefore, no one culture method can be utilized for all algae. Fortunately, the most commonly used species for laboratory purposes respond well to several different culture methods. Algae are broadly defined by their pigment color and are often described in color terms such as green, brown, red, brown-yellow, etc. Blue-green algae (cyanobacteria) are included here since their culture requirements more closely resemble algae than bacteria. Algae come in all sizes—from single-celled organisms to very large seaweed varieties. Algae are extremely useful for laboratory purposes and respond well to a few simple culture methods. Culturing/Media Upon arrival of algae cultures, loosen caps and aerate culture with a clean pipet. Caps should remain loosely in place to prevent contamination, yet permit free air exchange. In general, or if used within a week, cultures should receive diffuse not direct light. Since each culture is unique, see Selected Algae Culture Requirements table for specific media, temperature, and lighting requirements. Most algae grow well at 16–22 °C. A successful long-term culture medium for a specific algae must provide major nutrient salts, a usable source of nitrogen, a supply of carbon, and a suitable pH. In addition, temperature and light conditions must be maintained for successful growth. Maintain algae cultures in clean jars or in clean containers using the appropriate medium suggested for the specific species being cultured. Cultures should be placed in a window for light and loosely covered to reduce evaporation. For artificial lighting, use plant grow-lights or wide spectrum bulbs. Place cultures at a distance of 12–18 inches from the bulbs. Monitor the temperature of the culture—temperatures over 27 °C may be fatal for some algae species. Subculture to fresh media every six to eight weeks. Most commonly purchased algae cultures can be grown using the two generic media described below. (Bristol’s algae media and Knop’s Solution are available from Flinn Scientific.) Unique species may require more specialized media for optimal growth. A literature search is advised to determine the best medium to use for subculturing. VOLVOX - http://www.k-state.edu/olsonlab/volvox_media.html [http://srjcbiologybeckonsyou.wikia.com/wiki/Pringsheim%27s_Soil_Water Pringsheim’s Soil–Water] For culturing Euglena, before steaming add one-fourth of a softened pea seed, without the seed coat, to enhance growth. Bristol’s Modified Medium **Add another time** Prepare six stock solutions, each with one of the following salts dissolved in 400 mL of water. Sodium nitrate, NaNO3, 10 g Potassium phosphate dibasic, K2HPO4, 3 g Calcium chloride, CaCl22H2O, 1 g Potassium phosphate monobasic, KH2PO4, 7 g Magnesium sulfate, MgSO47H2O, 3 g Sodium chloride, NaCl, 1 g Combine 10 mL of each stock solution and dilute with 900 mL of distilled water. Add one drop of 1% iron(III) chloride solution (1 g iron(III) chloride in 100 mL of deionized water) and 40 mL of Pringsheim’s soil–water extract. Autoclave the mixture at 121 °C for 15 minutes. Selected Algae Culture Requirements Click HERE to see a table of general requirements. Disposal Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. Algae cultures may be disposed of according to Flinn Biological Waste Disposal Method Type I. Do not release lab cultures into local environment as some species may be invasive. Tips • The school cafeteria is usually a good source for large culture jars—be sure to clean them with soap and water before using. The bottom half of clear plastic two-liter bottles also work well for housing algae cultures. Once jars are brought into the laboratory, they should not be used again for food. • Excess media can be saved for future use if stored in a tightly sealed container in a dimly lit area. • Have students study prepared slides Category:Bio 10